1. Technical Field
The present invention relates to a noise attenuator which attenuates noise by producing a cancellation wave having a phase substantially opposite to a sound wave of the noise, and a vehicle air intake duct provided with the noise attenuator.
2. Description of the Related Art
A noise attenuator of the above-described type has conventionally been known in which noise is detected by a microphone and a cancellation wave having a phase substantially opposite to a sound wave of the detected noise is generated by an electric circuit and then output from a loud speaker (see Japanese Patent Application Publication No. JP-A-H05-46189, for example).
However, the aforementioned noise attenuator necessitates a dustproof or waterproof treatment and wiring processing in order to protect the electric circuit for generating the cancellation wave, resulting in a problem that installation thereof requires substantial time and cost.